Surgical stapling loading unit with stroke counter and lockout

ABSTRACT

A surgical loading unit for use with a handle assembly includes an elongate outer frame defining a longitudinal axis and having proximal and distal ends, an end effector mounted to the distal end of the outer frame, a drive at least partially disposed within the outer frame and operatively coupled to the end effector, and being adapted for longitudinal movement through a plurality of sequential firing strokes to operate the end effector and a rotatable counter mounted to the outer frame. The rotatable counter is adapted for rotational movement through an arc segment of rotation upon movement of the drive through each firing stroke, and has visual indicators for providing visual indicia corresponding to a number of firing strokes completed by the drive.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application which claims that benefit of and priority to U.S. patent application Ser. No. 14/812,353, filed on Jul. 29, 2015, now U.S. Pat. No. 10,064,622, the entire content of which is incorporated herein by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a surgical stapling apparatus, and more particularly, relates to a surgical stapling loading unit having a firing stroke counter and a lockout which locks the loading unit upon completion of a predefined number of firing strokes.

2. Background of Related Art

Surgical staplers for stapling tissue are known in the art and are inclusive of both single use and multiple use devices. Single use devices are preloaded with one or more staples and are disposed after a single use. Multiple use devices are disposed upon exhaustion of the supply of staples or completion of the surgical procedure. If the supply of staples is exhausted prior to completion of a surgical procedure, a new surgical stapler may be required to complete the surgical procedure. The use of additional surgical staplers for a single surgical procedure can be expensive.

In order to address the high expense associated with the use of multiple surgical staplers for a single procedure, surgical staplers with replaceable staple cartridges have been developed.

Covidien, LP, has manufactured and marketed stapling systems having replaceable cartridges, such as the Multifire ENDO GIA™ 30 and Multifire ENDO GIA™ 60 systems, for a number of years. These systems include a surgical stapling handle assembly and a surgical loading unit. The loading unit may be a single use loading unit (SULU) or a multiple use loading unit (MULU). The loading unit includes a body and an end effector, and is attached to the handle assembly immediately prior to surgery. The end effector may include a cartridge which houses a plurality of staples. After use, the loading unit can be removed relative to the handle assembly and replaced with a new loading unit to perform additional stapling and/or cutting operations. A drive assembly is supported within the loading unit and is engagable with a control rod of the surgical handle assembly to control operation of the loading unit.

Although these systems have provided significant clinical benefits, improvements are still possible. For example, it would be desirable to provide an improved stapling loading unit for use in a surgical stapling system which tracts the staple firing sequence to assist the clinician in monitoring the staple supply. It also would be beneficial to provide a surgical stapling device having a lockout to prevent firing of the device after the staple supply has been depleted.

SUMMARY

Accordingly, the present disclosure is directed to a surgical loading unit for use with a handle assembly. The surgical loading unit includes an elongate outer frame defining a longitudinal axis and having proximal and distal ends, an end effector mounted to the distal end of the outer frame, a drive at least partially disposed within the outer frame and operatively coupled to the end effector and being adapted for longitudinal movement through a plurality of sequential firing strokes to operate the end effector, and a rotatable counter mounted to the outer frame. The rotatable counter is adapted for rotational movement through an arc segment of rotation upon movement of the drive through each firing stroke, and has visual indicators for providing visual indicia corresponding to a number of firing strokes completed by the drive.

In one embodiment, the outer frame defines a window through which a visual indicator of the rotatable counter is visible. In certain embodiments, the rotatable counter includes a stop which is positionable to engage the drive upon rotatable movement of the rotatable counter through a predetermined number of arc segments corresponding to a predetermined number of firing strokes completed by the drive.

In embodiments, a counter actuator is mounted to the drive. The counter actuator is dimensioned to engage the rotatable counter to cause rotational movement of the rotatable counter through each arc segment of rotation during each firing stroke of the drive. The rotatable counter may include a helical gear having internal helical grooves. The counter actuator is engageable with the helical grooves to cause rotational movement of the rotatable counter. In certain embodiments, the counter actuator is adapted for pivotal movement relative to the drive, and is dimensioned to pivot out of engagement with the helical grooves of the rotatable counter during a return stroke of the driver subsequent to each firing stroke. The counter actuator may be adapted to pivot between an initial position and first and second pivoted positions. The counter actuator is engageable with one helical groove when in the first pivoted position during movement of the drive through each drive stroke, and disengaged from the one helical groove when in the second pivoted position during movement of the drive through each return stroke. In embodiments, the counter actuator is normally biased toward the initial position, and pivots in a first direction to assume the first pivoted position and pivots in a second direction to assume the second pivoted position.

In some embodiments, the outer frame includes a cam having rear and forward cam surfaces. The rear cam surface is engaged by the counter actuator during movement of the drive through each firing stroke to orient the counter actuator in the first pivoted position. The forward cam surface is engaged by the counter actuator during movement of the drive through each return stroke to orient the counter actuator in the second pivoted position.

The surgical loading unit may include a detent mechanism having a detent member mounted relative to the outer frame and locking recesses associated with the rotatable counter. The detent member is engagable with a respective locking recess subsequent to each firing stroke of the drive to maintain the rotatable counter at a desired angular or rotational position, and is adapted to release the respective locking recess upon movement of the drive through a successive firing stroke.

In certain embodiments, the end effector may include a fastener assembly including a plurality of fasteners with at least one fastener being ejected upon movement of the drive through a firing stroke.

In accordance with one embodiment, a surgical loading unit for use with a handle assembly includes an elongate outer frame defining a longitudinal axis and having proximal and distal ends and a staple assembly mounted to the distal end of the outer frame. The staple assembly has a staple cartridge housing a plurality of staples and an anvil. The anvil is adapted for movement relative to the staple cartridge between an open position to receive tissue and an approximated position to clamp tissue. A drive is at least partially disposed within the outer frame and operatively couplable to the staple assembly. The drive is adapted for longitudinal movement through a plurality of sequential strokes to eject at least one staple from the staple cartridge for crimping by the anvil when in the approximated position thereof. The surgical loading unit further includes a rotatable counter and lockout mechanism. The mechanism includes a rotatable counter mounted to the outer frame and adapted for rotational movement through an arc segment of rotation upon movement of the drive through each firing stroke, at least one visual indicator associated with the rotatable counter for providing visual indicia corresponding to a number of firing strokes completed by the drive and a lock member positionable to engage the drive upon rotatable movement of the rotatable counter through a predetermined number of arc segments corresponding to a predetermined number of firing strokes completed by the drive.

In embodiments, a counter actuator is mounted to the drive, and adapted to engage the rotatable counter to cause rotational movement of the rotatable counter through each arc segment of rotation during each firing stroke of the drive. The counter actuator may be adapted to pivot between an initial position and first and second pivoted positions. The counter actuator is engageable with the rotatable counter when in the first pivoted position during movement of the drive through each drive stroke, and disengaged from the rotatable counter when in the second pivoted position during movement of the drive through each return stroke. In certain embodiments, the rotatable counter includes a helical gear having internal helical grooves. The counter actuator is engageable with one helical groove when in the first pivoted position to cause rotational movement of the rotatable counter during each drive stroke, and disengaged from the one helical groove when in the second pivoted position during each return stroke.

In an embodiment, the loading unit includes a detent mechanism having a detent member mounted relative to the outer frame and locking recesses associated with the rotatable counter. The detent member is engagable with a respective locking recess subsequent to each firing stroke of the drive to maintain the rotatable counter at a desired angular or rotational position, and is adapted to release the respective locking recess upon movement of the drive through a successive firing stroke.

Further details and advantages of the outer and inner elastic members will be appreciated from the following written description.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with a general description of the disclosure given above and the detailed description of the embodiments given below, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a perspective view of a surgical loading unit for performing a surgical stapling procedure in accordance with the principles of the present disclosure;

FIG. 2 is a perspective view of the surgical loading unit mounted to a surgical handle assembly;

FIG. 3 a perspective view of the surgical loading unit with portions removed illustrating the central drive and the counter and lockout mechanism mounted relative to the central drive;

FIG. 4 is an enlarged isolated view of the area of detail identified in FIG. 3 illustrating the rotatable counter and counter actuator of the counter and lockout mechanism;

FIG. 5 is an exploded perspective view of the loading unit;

FIGS. 6-7 are perspective views of the rotatable counter of the counter and lockout mechanism;

FIG. 8 is a side cross-sectional view of the counter and lockout mechanism mounted relative to the outer frame;

FIG. 9 is an enlarged isolated view of the area of detail identified in FIG. 1 illustrating the window for viewing the visual indicators;

FIG. 10 is an enlarged isolated view of the area of detail identified in FIG. 5 illustrating the actuator holder and the counter actuator of the counter and lockout mechanism;

FIG. 11 is an exploded perspective view illustrating the actuator holder, the counter actuator and the torsion spring of the counter and lockout mechanism;

FIG. 12 is a perspective view of a detent mechanism for releasably securing the rotatable counter at select positions;

FIG. 13 is a cross-sectional view of another embodiment of a detent mechanism associated with the rotatable counter;

FIGS. 14-16 are cross-sectional views illustrating a sequence of movement of the counter actuator and rotatable counter during a firing stroke of the central drive;

FIG. 17 is a perspective view illustrating rotation of the rotatable counter during movement of the central drive during the firing stroke;

FIGS. 18-19 are cross-sectional views similar to the views of FIGS. 14-16 illustrating a sequence of movement of the counter actuator during a return stroke of the central drive;

FIG. 20 is a side cross-sectional view of the counter and lockout mechanism illustrating the rotatable counter in a lock position with an internal stop on the rotatable counter in engagement with a lock shelf of the central drive to lock the central drive;

FIG. 21 is a perspective view further illustrating the relationship of the internal stop of the rotatable counter and the central drive when in the locked position of the rotatable counter;

FIGS. 22-23 are cross-sectional views of the staple assembly with the staple cartridge and the anvil in respective open and approximated conditions;

FIG. 24 is an enlarged side cross sectional view of the staple assembly illustrating the staples fired from the staple cartridge during a firing stroke; and

FIG. 25 is a side cross-sectional view illustrating the staples fired upon completion of a firing stroke.

DETAILED DESCRIPTION OF EMBODIMENTS

Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are merely examples of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present disclosure in virtually any appropriately detailed structure.

Referring now to the drawings where like reference numerals indicate similar components throughout the several views, FIGS. 1-2 illustrate the surgical loading unit 10 in accordance with the principles of the present disclosure. In FIG. 1, the surgical loading unit 10 is depicted in isolation while in FIG. 2 the surgical loading unit 10 is depicted connected to a surgical handle assembly 200. The surgical loading unit 10 and the surgical handle assembly 200 form a surgical system adapted to perform a surgical procedure on tissue. The loading unit 10 includes an end effector 300 which, in one embodiment, is a stapling assembly adapted to staple tissue. The loading unit 10 may be a multi-use loading unit (MULU) adapted, e.g., for sequential or multiple firing of one or more staples in a linear arrangement.

The surgical handle assembly 200 may be any handle assembly having at least one actuator, and in some embodiments, two or more actuators adapted to control operation of the loading unit 10. It is contemplated that the surgical handle assembly 200 may be reusable, i.e., it can be reused with a plurality of loading units 10, and may be used with loading units having different stapling functions such as, e.g., circular stapling of tissue. The end effector 300 (shown in phantom in FIG. 1) may include a staple cartridge 302 which houses a plurality of staples and an anvil 304. The staple cartridge 302 and the anvil 304 are movable relative to each other between open and approximated positions. Staples are driven from the staple cartridge 302 through tissue and crimped by the anvil 304. Further details of the handle assembly 200 and the end effector 300 will be discussed in greater detail hereinbelow.

Referring now to FIGS. 3-5, in conjunction with FIG. 1, the loading unit 10 includes an elongate outer member or frame 12 defining a longitudinal axis “k” and proximal and distal ends 14, 16. In FIGS. 3-4, half of the outer frame 12 is removed for illustrative purposes. The proximal end 14 of the outer frame 12 includes a handle mount 18 (FIG. 1) with at least one mounting tab 20 which couples with the handle assembly 200. The distal end 16 of the outer frame 12 supports the end effector 300 (removed in FIGS. 3-5). A central beam or drive 22 is at least partially disposed within the outer frame 12. The central drive 22 is adapted for longitudinal movement within the outer frame 12 and is operatively couplable, at its proximal end, to an actuator of the handle assembly 200 and, at its distal end, to the end effector 300. The central drive 22 advances or moves distally, during a firing stroke, to control the end effector 300, e.g., by causing the firing of one or more staples. Subsequent to a firing stroke, the central drive 22 moves proximally, during a return stroke, to be in position for another firing sequence. The central drive 22 includes an actuation sled 24 at its distal end 16 and a knife 26 to sever tissue, e.g., during the stapling process. The knife 26 may be a component of, or coupled, to the actuation sled 24. The outer frame 12 may include a translating rod 28 extending along the longitudinal axis “k”. The translating rod 28 may be coupled to an actuator of the handle assembly 200 and to the end effector 300. The translating rod 28 may move in a longitudinal direction to control articulation (e.g., pivoting movement) of the end effector 300.

Referring now to FIGS. 3-7, the loading unit 10 includes a counter and lockout mechanism 30 for tracking the number of firings or firing strokes completed by the central drive 22 and lock the loading unit 10 upon completion of a predetermined number of firing strokes. The counter and lockout mechanism 30 includes a rotatable counter 32 and an actuator assembly 34. The rotatable counter 32 is adapted for rotational movement about the longitudinal axis “k” and within the outer frame 12. In one embodiment, the outer frame 12 defines an internal annular recess 36 (FIG. 5) which is dimensioned to receive the rotatable counter 32 in a manner permitting rotational movement of the rotatable counter 32 while restricting axial movement. As depicted in FIG. 8, the annular recess 36 may include a pair of annular ribs 38, which are received within corresponding dimensioned annular grooves 40 (FIG. 6) disposed on the external wall 32 e of the rotatable counter 32, to assist in securing the rotatable counter 32 from axial movement.

With particular reference to FIGS. 6 and 7, the rotatable counter 32 may include a helical gear defining a plurality of internal helical threads or grooves 42. Each internal helical groove 42 longitudinally extends along the length of the rotatable counter 32 in oblique relation with respect to the longitudinal axis “k”. The internal helical grooves 42 may encompass one-half the inner diameter or dimension of the inner wall 32 i of the rotatable counter 32 while the remaining portion of the inner wall 32 i is mostly smooth. The rotatable counter 32 may have twelve internal helical grooves 42 although more or less than twelve internal helical grooves 42 are also envisioned. The helical grooves 42 may be identical such when engaged by the actuator assembly 34 the rotatable counter 32 rotates through the same incremental arc segment of rotation.

The rotatable counter 32 includes visual indicia or indicators 44 on its external wall 32 e. The indicators 44 may include a plurality of numbers, e.g., 1-12, corresponding to a number of times the central drive 22 completes a firing stroke. Alternatively, the number may correspond to the number of firing strokes remaining with the loading unit 10. The indicators 44 are visible through a window 46 defined in the outer frame 12 (FIGS. 1 and 9). Upon movement of the central drive 22 through a firing stroke, the rotatable counter 32 is rotated to present the next subsequent indicator 44 for visualization through the window 46.

With continued reference to FIGS. 6 and 7, the rotatable counter 32 includes an internal stop 48 depending inwardly from the inner wall 32 i of the rotatable counter 32 in diametrical opposed relation to the internal helical grooves 42. The internal stop 48 is positionable to block advancement of the central drive 22 upon rotation of the rotatable counter 32 to a predefined angular orientation, e.g., to lockout the central drive 22 upon movement through a predefined number of firing strokes, which may correspond to depletion of, e.g., the staples in the end effector 300.

Referring now to FIGS. 4, 8 and 10-11, the actuator assembly 34 of the counter and lockout mechanism 30 will be discussed. The actuator assembly 34 includes an actuator holder 50 and a counter actuator 52 at least partially disposed within a channel 54 of the actuator holder 50. The actuator holder 50 is supported within a longitudinal opening 56 of the central drive 22 in fixed relation therewith (see also FIG. 5). Any methodologies for securing the actuator holder 50 within the opening 56 of the central drive 22 are envisioned. In one embodiment, the actuator holder 50 includes spaced longitudinal grooves or rails 58 which receive mounting segments 22 m of the central drive 22 (see FIGS. 8 and 10).

As best depicted in FIGS. 10 and 11, the counter actuator 52 is pivotally mounted within the actuator holder 50 through pivot pin 60 which extends through respective openings 62, 64 of the actuator holder 50 and the counter actuator 52. The counter actuator 52 may pivot in both a clockwise and counter clockwise direction about the pivot pin 60. A biasing member 66, e.g., a torsion spring, is mounted to the counter actuator 52 to normally bias the counter actuator 52 to an initial starting condition or stage of the counter actuator 52. The starting or initial stage of the counter actuator 52 is depicted in FIG. 10. The torsion spring 66 has one end 68 secured in an opening 70 in the counter actuator 52 and a second end 72 secured in an opening 74 (shown in phantom) in the actuator holder 50.

With reference again to FIGS. 4 and 5, the outer frame 12 includes a cam member 76 which cooperates with the counter actuator 52 to rotate the rotatable counter 32. The cam member 76 may be a separate component secured to the outer frame 12 or be integrally formed with the outer frame 12. The cam member 76 defines rear and forward cam surfaces 78, 80 and extends through the interior of the rotatable counter 32 in spaced relation therewith to not interfere with rotation of the rotatable counter 32. The cam member 76 defines an interior surface 76 i.

Referring now to FIG. 12, the loading unit 10 may include a detent mechanism to permit rotational movement of the rotatable counter 32 in a first direction through actuation of the counter actuator 52 while preventing rotational movement in a second opposite direction. In the embodiment of FIG. 12, the detent mechanism may include a spring loaded plunger 84 which is adapted for reciprocal longitudinal movement in the direction of directional arrows “c₁, c₂”. The plunger 84 may be mounted to the outer frame 12 by conventional means and defines a rounded plunger head 86. The plunger head 86 may selectively engage corresponding openings or recesses 88 in the distal face 32 d of the rotatable counter 32 during rotation of the rotatable counter 32 through each incremental arc segment of rotation. Each locking recess 88 may be in general alignment with a respective internal helical groove 42. Upon rotation of the rotatable counter 32, the plunger 84 is forced in a distal direction “c₁” such that the plunger head 86 is released from a select locking recess 88 and then returns under the influence of its spring bias in proximal direction “c₂” whereby the plunger head 86 is received within the next adjacent locking recess 88 in releasable secured relation therewith. In this position of the plunger 84, the rotatable counter 32 is prevented from rotating, and the successive internal helical groove 42 is positioned to receive the counter actuator 52. Upon movement of the central drive 22 and the counter actuator 52 through a successive firing stroke, the spring bias of the plunger 84 is overcome causing release of the plunger head 86 from the respective locking recess 88 permitting rotation of the rotatable counter 32 through a successive incremental arc segment of rotation. The plunger head 86 and the locking recesses 88 may have angled or cam surfaces to facilitate entry and exit of the plunger head 86 relative to the recesses 88.

FIG. 13 illustrates an alternate detent mechanism to permit movement of the rotatable counter 32 in the first direction while preventing movement in the second direction. In this embodiment, the external wall 32 e of the rotatable counter 32 includes a plurality of equi-distally spaced locking recesses 90 with each recess 90 in general alignment with a respective internal helical groove 42 of the rotatable counter 32. The outer frame 12 has a ratchet pawl 92 mounted thereto. The ratchet pawl 92 is normally biased toward the external wall 32 e of the rotatable counter 32 to engage a select locking recess 90. Upon rotation of the rotatable counter 32, the ratchet pawl 92 moves radially outwardly to release the select locking recess 90 and then returns under the influence of the spring bias to be received within the next adjacent locking recess 90.

The operation of the loading unit 10 and the counter and lockout mechanism 30 now will be discussed. With reference to FIG. 14, the central drive 22 is in its proximal or initial position and the counter actuator 52 of the actuator assembly 34 is in its starting condition or first stage under the normal bias of the torsion spring 66 (e.g., biased in a counter-clockwise direction). The loading unit 10 is coupled to the handle assembly 200 whereby a coupler 202 (shown schematically) of the handle assembly 200 couples with the actuator holder 50 and/or the central drive 22. An actuator of the handle assembly 200, which is operatively connected to the coupler 202, is actuated which initiates the first firing stroke of the central drive 22. As the central drive 22 and the actuator assembly 34 (including the actuator holder 50 and the counter actuator 52) move distally through the firing stroke in the direction “t”, the upper leg 52 u of the counter actuator 52 engages the rear cam surface 78 of the cam member 76, causing the counter actuator 52 to pivot or rotate in a clockwise direction “m” to its second stage shown in FIG. 15. In this position, the lower leg 521 of the counter actuator 52 is orientated to engage a first internal helical groove 42 of the rotatable counter 32. As depicted in FIGS. 16-17, during continued movement of the central drive 22 and the actuator assembly 34 through the firing stroke, the lower leg 521 of the counter actuator 32 traverses the internal helical groove 42 causing the rotatable counter 32 to rotate in the direction of directional arrow “b” through a predefined angular segment of rotation. The upper leg 52 u traverses the inner surface 76 i of the cam member 76 to maintain the counter actuator 52 in the engaged position. The central drive 22 is advanced (see arrow “t”) until the counter actuator 52 exits the internal helical groove 42 and clears the rotatable counter 32 as depicted in FIG. 18. In this position, the counter actuator 52 is reset or returns to its initial condition or first stage under the influence of the biasing member or torsion spring 66. Simultaneously therewith, the ratchet or detent mechanism of either FIG. 12 or FIG. 13 selectively secures the rotatable counter 32 at this angular position.

Subsequent to completion of the firing stroke, the central drive 22 and the actuator assembly 34 are moved proximally via, e.g., one of the actuators of the handle assembly 200 or via a spring bias, to initiate its return stroke. During the return stroke, the upper segment 52 u of the counter actuator 52 engages the forward cam surface 80 of the cam member 76 to rotate the counter actuator 52 in an opposite (e.g., counterclockwise) direction corresponding to a third stage of the counter actuator 52 depicted in FIG. 19. In the third stage, the lower segment 521 of the counter actuator 52 clears the internal helical grooves 42 of the rotatable counter 32 to permit the central drive 22 to complete the return stroke without engagement of the counter actuator 52 with the rotatable counter 32. The upper segment 52 u of the counter actuator 52 is in contact with the inner surface 76 i of the cam member 76 to maintain the counter actuator in the disengaged position.

The central drive 22 and the actuator assembly 34 may undergo successive firing strokes to, e.g., deliver all of the staples. During each stroke, the counter actuator 52 engages a subsequent internal helical groove 42 to cause rotation, e.g., incremental, of the rotatable counter 32 with the corresponding indicator 44 being viewable by the clinician through the window 46 of the outer frame 12. The ratchet or detent mechanism of FIG. 12 or FIG. 13 will secure the rotatable counter 32 at each incremental angular position, and then become released from the rotatable counter 32 during the next firing stroke and traversing movement of the counter actuator 52 through the successive internal helical groove 42.

With reference now to FIGS. 20-21, upon movement of the rotatable counter 32 through a predefined number of arc segments corresponding to a predefined number of firing strokes of the central drive 22, the rotatable counter 32 is eventually rotated to a position where the internal stop 48 is aligned with a lock shelf 82 of the central drive 22. In this position, the central drive 22 is locked and prevented from moving in a distal direction, i.e., incapable of firing. The locked position may correspond to depletion of the staples, e.g., in the end effector or staple assembly 300.

Thus, during use, the clinician can monitor the staple supply within the end effective 300 and anticipate when the supply will be exhausted. When the loading unit 10 is completed, the clinician can release the loading unit 10 from the handle assembly 200 and, if necessary, connect a new loading unit 10 to complete the procedure.

Referring now to FIG. 2, details of one exemplative handle assembly 200 for use with the loading unit 10 will be described. The handle assembly 200 includes a housing 204 and an elongated body 206 extending from the housing 204. The housing 204 includes a stationary handle 208 and a movable handle 210 which is pivotally supported to the housing 204 and is operatively connected to a control rod 212 extending at least partially through the elongated body 206. The control rod 212 is couplable to the central drive 22 of the loading unit 10 via, e.g., coupling 202, upon mounting of the loading unit 10 to the handle assembly 200. Pivotal movement of the movable handle 210 causes longitudinal translation of the control rod 212, which also may approximate the staple cartridge 302 and the anvil 304, and cause firing of the staples. A pair of retraction knobs 214 may be mounted to the housing 204 and also operatively coupled to the control rod 212. The retraction knobs 214 may be utilized to retract the control rod 212 and the central drive 22 of the loading unit 10 subsequent to each firing stroke. The handle assembly 200 may further include an articulation lever 216 which is couplable to the translating rod 28 of the loading unit 10. The articulation lever 216 may be manipulated to articulate the end effector or staple assembly 300. A rotatable knob 218 may also be provided to cause rotation of the elongated body 206 and at least the end effector 300 of the loading unit 10.

Other handle arrangements are also envisioned including single actuator handles, powered, electro-mechanical or the like. One example of a handle assembly 200 suitable for use with the loading unit 10 is disclosed in commonly assigned U.S. Pat. No. 8,070,033 to Millman et al., the entire contents of which are hereby incorporated by reference herein.

With reference now to FIGS. 22-25, further details of the end effector 300 of the loading unit will be discussed. In the embodiment of FIG. 1, the end effector 300 is a staple assembly including the staple cartridge 302 and the anvil 304 which are adapted to pivot relative to each other between open and approximated conditions depicted respectively in FIGS. 22-23. As best depicted in FIGS. 24-25, the staple cartridge 302 may include one or more staple magazines 306 with each magazine having a plurality of staples 308. Each magazine 306 may further include a staple cam 310 which moves in a direction generally orthogonal to the axis “k” to eject the staples 308 toward the anvil 304. At least one or more staple pushers 312 are at least partially disposed within the staple cartridge 302 and operatively coupled to the central drive 22 of the loading unit 10. (see also FIGS. 22-23) The staple pusher(s) 312 may be operatively couplable or engageable with, or a component of, the actuation sled 24 of the central drive 22. Movement of the central drive 22 through a complete firing stroke, e.g., actuation of the movable handle 210 of the handle assembly 200, will cause the staple pusher(s) 312 to engage the staple cams 310 to eject the staples 308 for passage through tissue to be crimped by the anvil 304. In one embodiment, the staple cartridge 302 will deliver at least two or more linear rows of staples. Simultaneously therewith, the knife 26 of the actuation sled 24 may sever the tissue between the linear rows of staples 308. Thereafter, the staple pusher 312 is returned through a return stoke to the initial position of FIG. 22 via, e.g., retracting movement of the retraction knobs 214 of the handle assembly 200. In this position, the movable handle 210 may be actuated to advance the control rod 212 and the central drive 22 of the loading unit 10 to deliver another set of staples 308 in sequence.

One exemplative staple assembly which may be incorporated with loading unit 10 is disclosed in commonly assigned U.S. patent application Ser. No. 14/279,781 to Kostrzewski, filed May 16, 2014, the entire contents of which disclosure are hereby incorporated by reference herein.

Although the end effector 300 is described as a stapling assembly, the loading unit 10 with the counter and lockout mechanism 30 may incorporate other types of end effectors with different functions. For example, the end effector 300 may be adapted to deliver any type of fasteners including clips, needles, medicant capsules or the like, and may be adapted to perform different stapling functions including end to end or circular fastening.

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described. 

What is claimed is:
 1. A surgical loading unit comprising: an outer frame defining a longitudinal axis, the outer frame having a proximal portion and a distal portion, the proximal portion adapted to be releasably coupled to a surgical device; an end effector supported on the distal portion of the outer frame; a drive at least partially disposed within the outer frame and operatively coupled to the end effector, the drive adapted for longitudinal movement through firing and return strokes to actuate the end effector; and a counter rotatably supported on the outer frame and movable in response to longitudinal movement of the drive, the counter having visual indicators to provide visual indicia that correspond to a number of the firing strokes completed by the drive.
 2. The surgical loading unit according to claim 1, wherein the outer frame defines a window through which at least one of the visual indicators of the counter is visible.
 3. The surgical loading unit according to claim 1, wherein the counter includes a stop, the stop positionable to engage the drive upon rotatable movement of the counter through a predetermined number of arc segments corresponding to a predetermined number of the firing strokes completed by the drive.
 4. The surgical loading unit according to claim 3, including a counter actuator mounted to the drive, the counter actuator adapted to engage the counter to cause rotational movement of the counter through each of the arc segments of rotation during each of the firing strokes of the drive.
 5. The surgical loading unit according to claim 4, wherein the counter includes a helical gear having internal helical grooves, the counter actuator engageable with the helical grooves to cause rotational movement of the counter.
 6. The surgical loading unit according to claim 5 wherein the counter actuator is adapted for pivotal movement relative to the drive, the counter actuator dimensioned to pivot out of engagement with the helical grooves of the counter during each of the return strokes of the drive subsequent to each of the firing strokes.
 7. The surgical loading unit according to claim 6, wherein the counter actuator is adapted to pivot between an initial position and first and second pivoted positions, the counter actuator engageable with one of the helical grooves when in the first pivoted position during movement of the drive through each of the firing strokes, and disengaged from the one helical groove when in the second pivoted position during movement of the drive through each return stroke.
 8. The surgical loading unit according to claim 5, wherein the counter actuator is normally biased toward the initial position, and pivots in a first direction to assume the first pivoted position and pivots in a second direction to assume the second pivoted position.
 9. The surgical loading unit according to claim 8, wherein the outer frame includes a cam having rear and forward cam surfaces, the rear cam surface being engaged by the counter actuator during movement of the drive through each firing stroke to orient the counter actuator in the first pivoted position, the second surface being engaged by the counter actuator during movement of the drive through each return stroke to orient the counter actuator in the second pivoted position.
 10. The surgical loading unit according to claim 1, wherein the end effector includes a fastener assembly having a plurality of fasteners, at least one of the plurality of fasteners being ejected upon movement of the drive through a firing stroke.
 11. A surgical loading unit comprising: an outer frame defining a longitudinal axis, the outer frame having a proximal portion and a distal portion; an end effector supported on the distal portion of the outer frame; a drive at least partially disposed within the outer frame and operatively coupled to the end effector, the drive adapted for longitudinal movement through firing and return strokes to actuate the end effector; and a counter rotatably supported on the outer frame and movable in response to longitudinal movement of the drive, the counter having visual indicators to provide visual indicia that correspond to a number of the firing strokes completed by the drive, wherein the counter is rotatably supported about the longitudinal axis of the outer frame.
 12. The surgical loading unit according to claim 11, including a detent mechanism having a detent member mounted relative to the outer frame and locking recesses associated with the counter, the detent member engagable with a respective locking recess subsequent to each firing stroke of the drive to maintain the counter at a desired rotational position, and adapted to release the respective locking recess upon movement of the drive through a successive firing stroke.
 13. A surgical loading unit comprising: an outer frame defining a longitudinal axis, the outer frame having a proximal portion and a distal portion, the proximal portion adapted to be releasably coupled to a surgical device; an end effector supported on the distal portion of the outer frame; a drive at least partially disposed within the outer frame and operatively coupled to the end effector, the drive adapted for longitudinal movement through firing and return strokes to actuate the end effector; and a counter rotatably supported on the outer frame, the counter having visual indicators to provide visual indicia that correspond to a number of the firing strokes completed by the drive.
 14. The surgical loading unit according to claim 13, including a counter actuator mounted to the drive, the counter actuator adapted to engage the counter to cause rotational movement of the counter through an arc segment of rotation during each of the firing strokes of the drive.
 15. The surgical loading unit according to claim 14, wherein the counter actuator is adapted to pivot between an initial position and first and second pivoted positions, the counter actuator engageable with the counter when in the first pivoted position during movement of the drive through each of the firing strokes, and disengaged from the counter when in the second pivoted position during movement of the drive through each of the return strokes.
 16. The surgical loading unit according to claim 14, wherein the counter includes a helical gear having internal helical grooves, the counter actuator engageable with one of the helical grooves when in the first pivoted position to cause rotational movement of the counter during each of the firing strokes, and disengaged from the one helical groove when in the second pivoted position during each of the return strokes.
 17. The surgical loading unit according to claim 14, further including a detent mechanism having a detent member mounted relative to the outer frame and locking recesses associated with the counter, the detent member engagable with a respective locking recess subsequent to each of the firing strokes of the drive to maintain the counter at a desired rotational position, and adapted to release the respective locking recess upon movement of the drive through a successive one of the firing strokes.
 18. A surgical loading unit comprising: an outer frame defining a longitudinal axis, the outer frame having a proximal portion and a distal portion; an end effector supported on the distal portion of the outer frame; a drive at least partially disposed within the outer frame and operatively coupled to the end effector, the drive adapted for longitudinal movement through firing and return strokes to actuate the end effector; and a counter rotatably supported on the outer frame, the counter having visual indicators to provide visual indicia that correspond to a number of the firing strokes completed by the drive, wherein the counter is rotatably supported about the longitudinal axis of the outer frame. 